Cooking nat-bar-nat food in an opposite-type pot

Question

The Star-K writes:

If one ate pareve food that was cooked in a fleishig [=meat] pot, one is not required to wait six hours before eating dairy. However, one may not eat this food together with dairy or reheat it in a dairy pot. For example, if one cooked spaghetti in a fleishig pot^[15] he may eat cheese immediately after finishing the spaghetti. However, he may not eat the spaghetti with cheese or with other dairy products. He should also not reheat the spaghetti in a milchig [=dairy] pot.^[16]

_{(See footnote 15 there for a more lenient exception when the meat pot hadn't been used for meat for a while. A more stringent exception (unmentioned there) AFAIK is when the pareve food being cooked is sharp.)}

Footnote 16 there says:

If he inadvertently cooked the spaghetti… in a dairy pot, a Rav [=rabbi] should be consulted.

1. Where does the restriction on reheating the pareve food in a dairy pot come from: who says it's forbidden? (The Rama 95:2, for one, doesn't, AFAICT.)
2. The footnote's saying to ask a rabbi seems to imply the permissibility of the food and/or pot depends on multiple factors: what are those factors?

Answer 1

1. The Mishbetzot Zahav,¹ in comment 4 to YD 95 , says (in disagreement with other authorities) that it is forbidden, ab initio, to cook pareve food in a meat pot with the intention of later re-heating it in a dairy pot. He says that this would be similar to "nullifying a prohibition ab initio," which is generally forbidden. Perhaps the Star-K wants to prevent this ab initio violation, but rather than get into the complications of intent and timing, just say "should not" (which is weaker than "may not" in the previous sentence) regarding the action that it's prohibited to intend - the final reheating in the opposite-oriented pot.

2. If I'm right that this is the Star-K's source for advising against reheating in the milk pot, they might say that the spaghetti and pot are both fine after the fact, but they don't want to rule accordingly in a lay-person's guide to prevent the ab initio violation. If this reheating did happen, the cook could consult a rabbi, who would rule that the food and pot are permitted.

   At least one additional consideration is whether the pot had sat idle for 24 hours since the last time it was used to cook dairy. Rabbi David Ortinberg of Berditchev (d. 1910) in Tehila L’Dovid (YD 20)² qualifies³ the ruling mentioned above, saying that if the milk pot had sat idle, then it is permissible to re-heat the spaghetti in it on purpose.

   There may well be other considerations. Anyone who's aware of them is welcome to edit them into this answer.

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<sup>1. Hat-tip to the Yeshiva Pirchei Shoshanim notes on this siman for this source.
2. This source also came from the YPS notes. Thanks to Fred for finding the biographical info and link.
3." ונראה דאם אינו ב"י מותר לבשל לכתחלה ליתנן בכלי שלהם. אבל לבשל לכתחלה באב"י של בשר לאכול בחלב עצמו ולהיפך פשיטא דאסור. וכן מבואר מלשון הרמ"א ז"ל בסמוך דדוקא כשכבר נתבשלו באב"י נוהגין היתר לכתחלה לאכלם עם מין השני. אבל לא לבשל לכתחלה."</sup>

Answer 2

Actually the Rama does kinda say that, all that is permitted according to the Rama is "ליתנן בכלי שלהם", which means putting the nat bar nat in the other min's utensil, however this clearly implies that if one were to cook it in the other min's pot, that would be problematic. Logically that would make sense too, since the reason behind the prohibition of eating nat bar nat that was cooked in a pot of the other min is because we view the act of cooking as a nat rishon and not nat bar nat, thus it would make sense that taking that food that's nat rishon and cooking it in other min's pot would be problematic as well, since obstensibly we view cooking with the other min as eating it with that min itself, so it would follow that cooking it with the other min would be tantamount to mixing it with the other min which is clearly prohibited according to the Rama. This is the view of the Yad Yehuda, although he only hints at this.

However, you are right that this is not at all obvious, since one can argue that all that was prohibited was to mix food that was cooked in a fleishig pot with actual dairy products, and that itself is only a stringency, to say that one can't cook that in a pot of the other min would be a stringency upon stringency. Indeed the R' Akiva Eiger in his notes (printed on the side in most modern editions under the name of השמטות) is unsure about this, but seems to say in the end that this is actually permitted. A clearer source on this is the Chamudei Daniel (Basar Vechalav din 37) which also clearly permits this. Hope that answers your question.